The present invention is directed to improvement of so-called collector type writing instruments, such as ball-point pens, felt tip pens, markers, fountain pens, small-tube writing instruments and the like, having a writing point at the front end thereof, an ink tank for directly storing ink and a collector or grooved adjuster for absorbing variation in internal pressure. In particular, the present invention relates to improvement of the mechanism to solve the flooding problem occurring when a collector type writing instrument is used under conditions in which a sharp pressure variation occurs such as on an airplane as well as to solve the forward leakage problem occurring when the tip is oriented downward.
Writing instruments which have a collector 6 as an internal pressure adjuster, disposed between a conventionally existing point assembly 1 and ink tank 3, for retaining free-state ink 2 and adjusting the pressure inside ink tank 3 so as to prevent forward leakage of ink from a tip 9 of point assembly 1 and ink flooding or leakage of ink 2 from an air hole 10 have been known (see FIG. 8).
A collector type writing instrument can adjust the internal pressure balance by holding ink 2 of a relatively low viscosity from ink tank 3 within retaining grooves 13 or fabric element formed as a retaining portion using capillarity, in collector 6 and returning ink to ink tank 3, meaning that it provides the function of protecting point assembly 1 from the influence of changes in pressure.
A collector type writing instrument has excellent performance such as capabilities of providing an ample amount of ink 2, securing the stable amount of ink flow down to the last drop and allowing for the amount of ink 2 left to be checked from the outside.
However, since the collector type writing instruments store ink 2 directly and allow movement in that ink 2 to and from collector 6, there is a serious drawback that ink 2 will flood outside through air hole 10 of the writing instrument there being no space for withholding ink 2, thereby polluting fingers or clothes if the writing instrument is exposed to an environment in which the ink inside collector 6 exceeds the maximum capacity of retention, which is the limitation of the internal pressure adjustment capacity. As the countermeasures for solving this problem or increasing the safety to some degree, it is possible to make collector 6 greater in capacity or make ink tank 3 smaller. There have already been writing instruments sold on the market which use a collector capable of preventing ink flood under usual environments, meaning gentle temperature changes and the like.
As the current situation is that collector type writing instruments use rather thick barrels, taking a safety margin into account, use of a thicker barrel than the present situation makes the instrument difficult to grip and loses the stylishness.
When ink tank 3 is made smaller, reduction of ink stored makes the life short. When collector 6 is made longer, the ink head H becomes higher when the normal collector 6 is made longer because the ink head H acting on point assembly 1 is proportional to the height from the air/liquid exchanger 18 to the tip 9 of writing assembly 1, hence forward leakage of ink 2 from tip 9 occurs.
On the other hand, when a writing instrument which has been capped under about 1 atm. on the ground and is uncapped inside an airplane in which the air pressure is generally reduced to about 0.8 atm., the interior of the pen which has been balanced under 1 atm., is instantaneously exposed to an environment of about 0.8 atm., so ink 2 inside moves in a rush and floods the space around the air channel 15 of collector 6, whereby ink 2 floods out from air hole 10, being unable to be properly retained by the whole part of retaining grooves 13.
In order to solve the flooding problem occurring under conditions in which the air pressure varies, devices and inventions have been disclosed in Japanese Utility Model Publication Hei 3 No.31580, Japanese Utility Model Publication Hei 3 No.31581 and Japanese Patent Application Laid-open Hei 9 No.104194, and others.
However, these disclosures only provide the function of blocking the flush to directly reach the air hole, which is not efficient enough, hence a further effective improvement or other ways to reach a solution have been demanded.
Further, since collector type writing instruments have the problem that the life of writing abruptly ends when ink 2 runs out, it is necessary to carry a spare if the writing instrument has a low amount of ink. There is a demand for collector type writing instruments which can provide an ample amount of ink, which is the main feature of collector type writing instruments, until nearly the end of writing and can provide the performance of a fabric sliver type instrument, which delivers gradually reducing amounts of ink, for a short time so that the pen can be used to take some notes after the last drop of ink 2 is used up. There is another problem of ink dropping from the writing point making it difficult to write when the pen has been kept upside down for long time. Further, even when an equal amount of ink is loaded, a collector type writing instrument delivers a greater amount of ink than a conventional fabric sliver type writing instrument and hence has a shorter life. Therefore, there is a demand that downsizing of the ink tank volume should be avoided as far as possible.
As the solution to the aforementioned ink drop problem and the like, devices and inventions as to writing instruments having a fabric sliver or sponge therein have been disclosed in Japanese Utility Model Application Sho 59 No.184682, Japanese Utility Model Application Laid-open Hei 5 No.2990 and Japanese Utility Model Publication Hei 7 No.8234, and others.
These mainly aim at the means for a solution of the ink drop problem. When the pen is used for writing under conditions in which free-state ink 2 is used up while an ample amount of ink 2 resides in the sponge or the like, air enters into tank 3 through air/liquid exchanger 18. In this situation, when writing with the pen has been stopped and it is left with its tip downward (in a state of rest taking while writing), it happens that ink 2 remains fed to point assembly 1 from the sponge or the like, despite the fact that no free-state ink stays at air/liquid exchanger 18 and hence no reduction in internal pressure due to a meniscus occurs.
Since, in this state, head HS of ink 2 from tip 9 to the upper end of the sponge is applied on tip 9 of point assembly 1, forward leakage of ink 2 from tip 9 is liable to occur. This situation is almost equivalent to a case where the space of the fabric sliver of a conventional sliver type writing instrument is filled up with ink up to fully 100%. For actual, conventional sliver type writing instruments, ink is initially loaded only up to about 80% so as to avoid this situation.
When an ink absorber 31 such as sponge, fabric sliver or the like is inserted into a free-ink collector type writing instrument, the above situation, that is, the 100% ink loaded state, will inevitably occur in the process of ink 2 being consumed. Therefore, if an ink absorber 31 consisting of a small fabric sliver etc. is used as the countermeasure against sharp changes in pressure, which is the main object of the present invention, a solution to this problem should be also found.
It is therefore a main object of the present invention to provide improvement of collector type writing instruments of prevalent configurations. In detail it is a main object of the present invention to provide a writing instrument which, without the necessity of a special configuration limiting the usage, can avoid crucial accidents such as pollution of consumer""s clothes and fingers, due to forward leakage of ink 2 from tip 9 of point assembly 1 or due to flooding of ink 2 from air hole 10 exceeding the limit of the pressure adjustment capacity of collector 6, by alleviating the variation in pressure inside ink tank 3 resulting from change in temperature or air pressure.
There has been a demand for solution to the defect of collector type writing instruments, i.e., the liability to cause flooding especially when they are used on an airplane or under an environment in which sharp temperature change occurs. Therefore a further enhanced writing instrument can be obtained if an inexpensive collector type writing instrument with the above problem removed can be provided while the appearance and writing distance (life) are kept as before, if a solution to the forward leakage problem under the situation where no free-ink remains while an ample amount of ink 2 remains within ink absorber 31 is solved, and if the end of writing life problem and ink drop problem can be solved.
In general, collector type writing instruments include ball-point pens, fountain pens, small-tube writing instruments and the like which have an ink feeder core (center core 8, collector core, and the like) for assuring the flow path of ink 2 having a low viscosity (100 mPxc2x7s or lower) from an ink tank 3 to a writing point 9 provided at the tip of a point assembly 1 or which have an ink feeder portion made up of a slit (in the case where a vertical groove 14 is extended to the tip) and the like in a collector 6, and felt tip pens, markers and the like in which ink feeder core (7, 8) itself serves as a writing tip 1. Hereinbelow, ink feeder cores (center core 8, collector core 7, etc.) will also include those which themselves serve as pen tips.
Arranged between ink tank 3 of a cup-like shape having a bottom integrally formed or assembled with a separate part such as a tail plug or the like and a point assembly is a collector 6, which may be formed of a plurality of retaining grooves 13 (generally, gaps defined by a plurality of vanes 12), an air groove 15 connected to the external air and a narrow longitudinal groove 14 creating communication between retaining grooves 13 or which may be made up of surface treated fibers, so as to retain ink 2 using capillarity. An air/liquid exchanger 18 of a small enough size is provided for collector 6 and is adapted to be wetted with ink 2, so that ink tank 3 can be isolated from the external air and air will not enter ink tank 3 from the outside other than through air/liquid exchanger 18.
In the present invention, the above-stated typical configuration of a collector writing instrument is provided while, as an effective means of the present invention, an ink absorber 31 made up of a fabric sliver, sponge, fiber bundle, foamed material, or the like capable of retaining ink is incorporated in ink tank 3 and connected to center core 8, collector core 7 or longitudinal groove 14, in order to lead ink 2 from the interior of ink tank 3 to writing point 9 of point assembly 1.
Since, while free-state ink 2 remains in ink tank 3, ink 2 from center core 8, collector core 7 and the front and rear ends of ink absorber 31 flows in, the same writing performance as a conventional collector writing instrument can be obtained.
When free-state ink 2 is used up, the writing performance becomes close to that of a conventional sliver type configuration. To avoid spoiling the excellent writing comfort of a free-ink type collector type writing instrument, it is preferred that appropriate countermeasures such as reducing the ink absorber 31 in size, setting the capillary capacity of ink absorber 31 lower than that of center core 8 and collector core 7, or other methods are taken.
Ink absorber 31 is configured so that its length at least reaches to a position more rearwards than the approximate center of ink tank 3 and its diameter is sized so as to create a space around itself for permitting free-state ink 2 to move freely while it can absorb ink 2 at least from both the front and rear ends.
As ink absorber 31, a fiber bundle core which is formed by bonding or forming ordinary fibers with adhesives or with heat, a fabric sliver made up of soft fibers covered by a cladding, a shaped mass of foamed sponge and others can be used.
In order to use ink 2 efficiently and to avoid spoiling the excellent writing comfort of a free-ink type collector type writing instrument, necessary methods such as reducing the capillary capacity lower than that of center core 8 and collector core 7 may be employed as appropriate.
As an effective configuration of the present invention, an ink lead portion 39 which permits ink 2 absorbed in an ink absorber 31 to flow to an air/liquid exchanger 18 when free-state ink 2 is used up is provided for a collector 6. Specifically, lead portion 39 is configured so as to be able to provide capillary capacity by a combination of an ink lead channel 40 and other parts, and is arranged to connect between ink absorber 31 and air/liquid exchanger 18.
Lead portion 39 may be inserted into the front end part of ink absorber 31 or may be configured so as to lead ink in an indirect manner by its being brought into contact with collector 7, center core 8 or the like that serves as an ink feeder portion from ink absorber 31 to writing point 9, instead of being directly connected to ink feeder 31.